I'm going straight to the main problem: the author has no idea how to make a worldbuilding or handle power creep. The fights are interesting, but the powerscale is so confusing and everytime the characters gain power when it's convenient to the plot. The politics of this world makes no sense and the 99% of the characters don't have a believable motivation after the first 100 chapters.
Have you ever played final fantasy? One of the funniest things in final fantasy that every final boss become a god in the final and the final fight is amazing compared to the rest.
The god of highchool want's to make EVERY FIGHT looks like a final fantasy final boss fight, and it doens't work, because if every fight is incredible, it become predictable and boring.